Tumors, especially malignant cancerous tumors, are the leading cause of death in humans. Although tumor biology and medical oncology has been greatly developed, such as through the discovery of tumor biomarkers, convenient surgical procedures, and development of radiotherapy and chemotherapy, overall cancer survival has not had significant improvement. In order to improve survival rates and the quality of life of patients suffering with cancer, we have continued to develop new methods for early diagnosis and treatment of cancer.
Today, there is a great challenge in the development of tumor-targeting nanoprobes. Compared with the most conventional method in the field of oncology, it is possible for molecular imaging to detect progression of the disease or treatment efficacy earlier. Fluorescence imaging and Raman imaging draw special attention from medical diagnosis, owing to their high sensitivity, and could provide quantitative and dynamic bioinformation. With the continuous deepening of study and improvement of the system, fluorescence imaging and Raman imaging techniques can quickly measure tumor growth of a variety of cancer models, as well as timely observe and assess changes of cancer cells during cancer treatment. Further, they may quantitatively detect in situ tumors, metastatic tumors, and/or spontaneous tumors in mice as a whole.
For example, Hollingshead et al. constructed U251-HRE cells using human glioma cell line U251, and implanted this tumor cell into nude mice. They found that when tumors reached 300-500 mg, hypoxia occurred in local tissue. At this point, a significant expression of luciferase can be monitored. This method not only monitored the tumor itself, but more importantly could monitor the microenvironment where tumor cells are located. Additionally, fluorescence imaging and Raman imaging techniques can provide precise information of molecular characteristics and changes of cells and tissues, and can reveal histomorphologic and anatomical details through spectral fingerprints of molecular structure and location. Thereby, they can serve as clinical diagnostic tools to help medical professionals detect disease and response to treatment at the molecular level.
Developments in nanoscience and nanotechnology has facilitated the advancement of nanomaterials used for molecular imaging and cancer therapy, and has promoted the development of nanodevices for use in cancer detection and screening. Moreover, nanomaterials can not only provide highly sensitive and specific imaging information of cancer patients, but can also deliver anticancer drugs to site of the tumor. In addition, some of nanomaterials themselves can be used as drugs for treatment of cancer. However, our understanding on the following areas is still limited: biomarkers suitable for imaging; selection of materials for imaging target and contrast enhancement; and chemical methods used for imaging of bioprobes. We have also encountered difficulties in the development of cancer-specific imaging agents, including: suboptimal transport of probes targeting tissue or tumor; great biological toxicity; poor stability of the probe; low intensity of in vivo signal enhancement.